The present invention relates to a permanent magnet embedded rotor for a rotating electric machine and a rotating electric machine.
A rotor core for a permanent magnet embedded rotor includes a plurality of embedded permanent magnets. The permanent magnets form a plurality of magnetic poles. Each adjacent pair of the magnetic poles is different from one another as disclosed in FIG. 1 of Japanese Laid-Open Patent Publication No. 2008-211934. Thus, the magnetic fluxes are likely to be short-circuited between the ends of each adjacent pair of the permanent magnets. As more short-circuited magnetic fluxes occur, less torque is produced.
A rotor core disclosed in FIGS. 11 and 12 of Japanese Laid-Open Patent Publication No. 2004-104962 has cavities each serving as a flux barrier. The flux barriers are each adjacent to the end of a permanent magnet and open through a rotor outer circumferential surface serving as the outer circumferential surface of a rotor core. This reduces short-circuited magnetic flux between adjacent permanent magnet ends.
As described by Japanese Laid-Open Patent Publication No. 2004-104962, an adjacent pair of permanent magnets of symmetrical polarity arrangements has the magnets arranged in a V shape. The V shape increases a core zone between the permanent magnets of symmetrical polarity arrangements and the rotor outer circumferential surface. This increases magnet torque. The two adjacent permanent magnets of symmetrical polarity arrangements are accommodated in two corresponding magnet insertion recesses, or, in other words, magnet accommodating portions. The magnet inserting recesses are shaped in correspondence with each permanent magnet, which has a flat plate-like shape. The flux barrier, which is a cavity, is a space extending longitudinally from each magnet insertion recess.
However, in the above configuration, in which each pair of the permanent magnets are arranged in the V shape, the aforementioned core zone is supported only by a bridge portion as a core portion between the magnet insertion recesses. When the rotor core rotates, the centrifugal force acting in the core zone is applied to the bridge portion as load. As a result, if the core zone is large, the centrifugal load on the bridge portion may become excessively high.
Accordingly, it is an objective of the present invention to decrease centrifugal load acting on a bridge portion between each pair of adjacent permanent magnets having symmetrical polarity arrangements.